1. Technical Field
The purpose of this invention is a process for collective production of integrated magnetic heads with a determined height of the supporting surface.
Its applications are the production of helical recording heads on a magnetic tape, particularly for video recordings for the general public and for professional applications (VCRs for the home, camescopes) and for equipment used to save computer data on tapes or disks.
High frequencies made possible by the small size of heads integrated in thin layers enable digital recording (for example according to the DVC standard for video, or the DDS standard for data processing). Computer mass memories including tape data recorders have the highest storage capacities and the lowest costs. Computer applications include data archiving systems, backups of hard disks for a system or a network for the distribution of large software or data bases. VCR video recording applications could be extended to include applications for a video server on which several films are stored centrally.
2. State of Prior Art
FIGS. 1 to 3 attached illustrate the structure of a component for an integrated magnetic head with thin layers according to document FR-A-2 747 226. As illustrated in FIG. 1, the head comprises two polar parts 101, 102 separated by an airgap 14, two magnetic arms 161, 162 partly covering the polar parts, and a magnetic flux closing part 18. All of these parts form a magnetic circuit. Conducting windings 201, 202, are placed around the arms 161, 162, not shown, to read and/or write the information written and/or read on a recording support.
FIG. 2 shows the complete head with two conducting strips 221, 222 used to access conducting windings 201, 202 and two electrical connection pins 241, 242.
The head shown in FIGS. 1 and 2 may be made collectively using techniques taken from micro-electronics. The components can be separated from each other by storing them in a matrix structure and then cutting them along straight lines, in order to obtain an individual magnetic head from a plate containing a number of components. A rounded supporting surface necessary for correct operation of the head is obtained by machining the front part of the components of each head close to polar parts 101, 102. In FIG. 2, the rounded profile is shown diagrammatically by line 26. This operation is carried out mechanically on each head.
FIG. 3 diagrammatically shows a longitudinal section along one of the conducting strips of a head and one of the arms of the magnetic circuit. It shows a substrate 30, for example made of silicon, with one of the polar parts 101 or 102, a magnetic arm 161, or 162, a magnetic closing part 18, a conducting strip 221, or 222 and electrical connection pins 241, 242. The assembly is covered by a superstrate 40, for example made of silicon. The supporting surface 26 near the front of the head has an appropriate rounded shape. Towards the back, the superstrate 40 is exposed to show the electrical connection pins 241, 242.
The substratexe2x80x94superstrate assembly may be thicker than the thickness required for the supporting surface. For example, 500 xcexcm thick silicon substrates and 300 to 500 xcexcm superstrates are used frequently, although the thickness of polar parts at the supporting surface must not exceed about 300 xcexcm. This is why the magnetic head is thinner at polar parts, as shown in FIG. 3, where it can be seen that the height h of the supporting surface is less than the thickness of the assembly. This makes the contact between the head and the recording support more intimate.
A helical recording head on a tape with a thickness of a few hundred micrometers may be made thinner, for example to a value of between 40 and 80 xcexcm.
The head is thinned individually on each head, which is obviously expensive. Furthermore, this operation is very difficult and could irreparably damage the head, seriously reducing the production efficiency.
The purpose of this invention is to correct these disadvantages.
Consequently, the invention suggests a process in which thinning is done collectively and no longer individually. Therefore, the cost is lower and the efficiency is better.
More precisely, the purpose of the invention is a process for the collective production of integrated magnetic heads that consists of making several components on a board, each with specific means capable of forming at least one magnetic head, these means comprising in particular polar parts separated by an airgap, and separating the components at the end of the process to obtain heads with an appropriate shaped supporting surface, this process being characterized in that the components are collectively thinned by etching the board in a direction perpendicular to the plane of the board along areas overlapping the polar parts, the individual heads thus obtained having a supporting surface with a low determined height in the said direction.
The thinning operation may be done by photolithography or by mechanical etching or by a combination of these two techniques.